Obesity is a major risk factor for obstructive sleep apnea (OSA), a condition characterized by repetitive respiratory disturbances, intermittent hypoxia, sleep fragmentation by frequent microarousals and low amounts of deep slow wave sleep [SWS]). Today, more than 10 million American women suffer from OSA. OSA has been identified as an independent risk factor for the metabolic syndrome. Because OSA is more prevalent in men than in women, a disproportionate number of studies of OSA and its consequences have been conducted in men. Thus, OSA has been characterized as a disorder associated with gender-based health care inequity. Recent evidence, including data from our group, suggests that reduced amounts and intensity of SWS (i.e.slow-wave activity [SWA]) may play a pivotal role in the development of metabolic and cardiovascular disturbances in obese men and women, particularly those with OSA. The present project will focus on sex differences in SWA and their relationship with daytime sleepiness and metabolic vulnerability in obese men and women with and without OSA. We propose to simultaneously characterize: 1. sleep-wake regulation; 2. measures of diabetes risk 3. measures of cardiovascular risk and 4. profiles of sex steroids, cortisol and adipokines in a. obese men without OSA, b. obese men with OSA before and after treatment with continuous positive airway pressure (CPAP), c. obese pre-menopausal women without OSA, and d. obese pre-menopausal women with OSA before and after CPAP treatment. The completion of these interdisciplinary studies will provide a unique data set contrasting in obese women versus obese men the relationships between sleep and the metabolic syndrome, OSA and the metabolic syndrome and the impact of CPAP treatment on the metabolic syndrome. The proposed work will provide important insights regarding the pathophysiology of OSA and its adverse consequences in obese men and women, and the basis for the development of effective sex-specific prevention and treatment strategies.